bigtee95vette

my mechanic uses Castrol GTX synthetic. Has anyone used it, and is it as good as Mobil 1?

RollaMo-LT4

Anytime you bring up the subject of which oil is better or "best", you will get opinions all over the place.
It always comes down to a personal preference.

My opinion, is yes the Castrol GTX synthetic is just as good as Mobile 1
And I've never used the Castrol.

After all these years, it really isn't going to make much difference in what oil you use.
Routine fluid changes and normal maintenance are much more important than what brand you end up using.

vader86

Without a lab analysis of one vs the other I see no reason to say GTX Syn is any worse or better.

If you take care of your engine, run the right weight, and change it regularly with a good filter, it doesn't so much matter.

I have used the M1 synthetic exclusively in the corvettes but I have used GTX and GTX syn in other vehicles and have no complaints on either.

PLRX

Few C6Z06 have done the Royal Purple Vs. Mobil 1 analysis, and M1 came on top. On the Bob is the Oil Guy forum, M1 is also above RP.

I think oils are now like gasolines. All gas commercials tell us they provide the best miles per gallon. In reality the top MPG gasolines I ever used were ethanol free Conoco, Tesoro, and Texaco. On the 10% ethanol category it would be Sunoco.

I use Mobil 1 because its easier to find, and cheaper than Royal Purple.

What I hear a lot from many mechanics is "Don't use that synthetic crap"

Tom400CFI

^Right here^.

Plus, virtually any oil that you can buy today, is better than the oils that were available when these cars were built. In short, change the oil when it's needed, you can't lose.